A typical seat device for vehicles is equipped with a power transmitter, such as a height brake, for adjusting the position of the seating surface. The power transmitter is provided with an operating lever. The operating lever is vertically moved to drive the power transmitter, thereby adjusting the position of the seating surface of the seat device. Unfortunately, if a force greater than the expected is applied to the operating lever, it may be also applied to the power transmitter.
Recently, a technology has been developed that prevents the application of a force greater than a predetermined level to the power transmitter by providing a torque limiter on the operating lever (see, for example, Patent Document 1). More specifically, an operating lever consists of a body of the lever and a grip. A first U-shaped spring groove extends along the side surface near the tips of the body of the lever. A second U-shaped spring groove extends along the side surface near the roots of the grip. The ends of the first U-shaped spring groove face the ends of the second U-shaped spring groove. The operating lever is assembled by coupling each end of the first U-shaped spring groove to the corresponding end of the second U-shaped spring groove with a hinge. The operating lever includes a torque limiter. The torque limiter is formed by an elongated and thin flat spring. The flat spring has a curved surface along a width direction thereof. The flat spring is disposed between the first and second U-shaped spring grooves, which are formed in the body of the lever and the grip, respectively, such that the curved concave surface faces the exterior. The flat spring is wound along the first and second U-shaped spring grooves as needed and is fastened so as not to be loosened.
According to the technology disclosed in Patent Document 2, a lower rail (26) is provided on the floor of a passenger compartment. An upper rail (24) is provided along the lower rail (26) such that it can move in the front-back direction. A bottom seat (seat device cushion 12) is disposed above the upper rail (24). A shift lifter (22) is disposed between the upper rail (24) and the bottom seat (12). A backrest (seat device back 14) is erected at the rear end of the bottom seat (12). The seat lifter (22) lifts up or lowers the bottom seat (12). The side surface of the bottom seat (12) is covered with a cover (42). The seat lifer (22) is disposed on the interior of the cover (42) and covered with the cover (42). An operating lever (32) is disposed on the exterior of the cover (42). The operating lever (32) has a rear end (32A) which bulges outward. A power input member (22G) of the seat lifter (22) extends through the cover (42) from the interior to the exterior. The rear end (32A) of the operating lever (32) is coupled to the power input member (22G) of the seat lifter (22) outside of the cover (42). When a user pulls up the operating lever (32), the seat lifter (22) lifts up the bottom seat (12). When the user presses down the operating lever (32), the seat lifter (22) lowers the bottom seat (12). Unfortunately, the technology disclosed in Patent Document 2 cannot stabilize the posture of the operating lever (32) because of its long length and vibrates in the right-left direction around the rear end of the operating lever (32). At the operation of the operating lever (32) by the user, the operating lever (32) is interfered by the cover (42). In other words, the operating lever (32) comes into contact with the cover (42) or generates friction with the cover (42) to cause resistance to the movement of the operating lever (32).